The rules state that if you are not able to win combat on your own, you may ask any other player to help. My question is, can other players offer to help without being asked? Specifically, can other players underbid when a bribe has already been offered to a specific player?

Example: I ask player A to help for 1 treasure, player B shouts "I'll help for free!"

The rules state that if you are not able to win combat on your own, you may ask any other player to help. My question is, can other players offer to help without being asked? Specifically, can other players underbid when a bribe has already been offered to a specific player?

Example: I ask player A to help for 1 treasure, player B shouts "I'll help for free!"

Yes, all of that is OK -- but once you have *accepted* help, it's too late to back out.